Hemostatic/fibrinolytic protein changes in C3H/HeN mice infected with Rickettsia conorii - A model for rocky mountain spotted fever

Changes in plasma hemostatic and fibrinolytic proteins were determined duri ng courses of a murine model of fatal and non-fatal Rocky Mountain spotted fever. C3H/HeN mice were infected with Rickettsia conorii and coagulation a nd histopathologic studies were performed at prescribed periods of time, A significant decrease in plasma factor VIII activity and rise in plasma fact or V procoagulant activity correlated with a fatal infection. Factor VII le vels were unchanged; factor XI levels dropped early in the course in the le thally infected animals, but returned to normal. Factor XII, high molecular weight kininogen, and prekallikrein levels were unchanged by the sublethal infection. Prekallikrein levels fell during the lethal infection. Antithro mbin concentrations were decreased significantly in all animals, but plasma plasminogen levels did not change in either group of animals. Nonocclusive thrombi were microscopically observed rarely and only in animals surviving a sublethal infection. A fall in tissue plasminogen activator activity and a rise in plasminogen activator inhibitor activity highly correlated with a lethal outcome. Lethal infection with R. conorii is associated with prima ry endothelial cell injury resulting in decreased tissue plasminogen activa tor and increased plasminogen activator inhibitor.